There's a very nice one at a decent price right now on Reverb:
Ibanez LA Custom Shop SDGR 5-String Fretless Bass - Natural https://reverb.com/item/92379215
I was waiting for THAT comment.
And it was such a success that Ibanez decided to stop the production of headless basses just after for a very, very, very long period.
With a latency of 40 years for the both of them...
I've been playing mostly headless fretless sixers over around the same period, so Ibanez and Dingwall are a bit late to the party, aren't they.
My 1978 fretless Stingray looks ace in natural finish with full chrome hardware.
Just give the full chrome a try first and then decide to go full black afterwards should you still want it.
That said, in ancient times, Musicman used to do swaps ... maybe it could be worth really insisting on this point.
This the way they have been protecting themselves from copies and fakers over the years, and it's working pretty well.
At least, when you buy an old Musicman you know you're buying the real deal ... most of the time, unlike Fender, for instance.
Atlansia built something like this with this Oxford, not exactly what you described, but an attempt to have almost any possible sound by selecting any of the 16 pickups/coils:
Yes, I did a few times over the years.
As I don't really use the placement from the bridge because of its inherent inaccuracy, I've always let it in inches and never mattered.
Use the nut as a guidance for a more accurate position.
Check this file where there is a lot of pickup placements including Fender and Musicman (4 or 5 string pickup is the same position): Pickup Positions For Many Makes Of Bass.xlsx
The Roland GK3B is indeed an hexaphonic (per se a pickup for each string) pickup like ALL so-called MIDI pickups @ped, but it allows you to use a MIDI system so is often referred as a MIDI pickup for some reason.
It was not @Rosie C enquiry. 😉
I did many times, but it always ended with a whole resale as I didn't see the point of all this.
That said, it works very well latency wise and I don't see why it wouldn't work with a fretless bass as it's only about converting a note into data for the MIDI system.
Listen to Uzeb and Alain Caron as he's been using (6) strings MIDI fretless basses since the beginning in the ... 80's (when the latency was delirious especially with a low B).